The present invention is directed to microfabricated devices, to methods of manufacturing the microscale devices, and to methods of detecting a chemical change, a physical change, a chemical agent, or a biological agent using the microscale devices. In particular, the devices are manufactured from a substrate having microscale fluid channels, and polymerizing one or more polymerizable mixtures in the channels to form the operating components of the device. The method of manufacture eliminates the traditional assembly of individual microscale components to form the device.
Current methods of manufacturing microscale devices, like microfluidic devices such as valves, pumps, and actuators, typically parallel, and are extensions of, macroscale design, manufacture, and assembly processes. For example, lithographic processes are used to add material to, or subtract material from, a substrate. The parallel approach to manufacturing microscale devices has retarded the development of complex microscale devices, especially because of difficulties in microscale device assembly, long development time, and high cost.
Presently, two approaches typically are used in the manufacture of microscale devices. The first is a true integrative approach in which lithographic processes are used to fabricate all required device components using a single process, e.g., polysilicon surface micromachining. In the second approach, fabrication of individual components is followed by component assembly to form the device. In this approach, assembly of the microscale device is identical to the assembly of a macroscale device, except uncommon methods are required to assemble microsized components. For example, slurry assembly is one method of assembling microscale components to form a microscale device.
Research in the area of microelectromechanical mechanical (MEM) systems has provided many examples of microfluidic devices and components, like miniaturized pumps and valves. Many types of microscale valves have been manufactured, including passive and active valves. However, the integration of microscale valves and other microscale components into microfluidic devices has proved difficult because a manufacturing process that provides a useful valve often is different from a manufacturing process that provides a useful pump or sensor. In other words, different device components often require different materials of construction and different types of manufacturing steps, thereby making integration of several microscale components into a single device difficult.
As stated above, two general methods of manufacturing microscale devices currently are used. Either the components are built separately, and then assembled to form the microscale device, much like assembly of a macroscale device, or traditional lithographic techniques are used to manufacture all the components of the device. The assembly approach is difficult at the microscale range for readily apparent reasons (e.g., the micron range size of the components makes handling and assembly difficult). In addition, electrostatic and other surface forces become dominant at the small size of the microscale components, thereby making manipulation of the components difficult. Lithographic processes overcome some of the problems associated with the assembly process, but integration of multiple components into a single device is hindered by the several disparate materials of construction and manufacturing methods often required to manufacture the different individual microscale components of the device.
Investigators have studied other microscale fabrication methods including fabrication of metal wires in channels, folding conductive polymer boxes, microstamping and micromolding, and two photon polymerization, but many of the above-mentioned problems associated with the manufacture of microscale devices have not been overcome. For example, T Breen et al., Science, 284, pp. 948-951 (1999) discloses in-channel fabrication techniques that utilize laminar flow to create textured walls and to position metal traces within microchannels. Smela et al., Science, 268, pp. 1735-1738 (1995) discloses conductive microscale actuators built by lithographically patterning conductive polymers on flat substrates. Two-photon polymerization has been used to provide three-dimensional structures from a polymer gel precursor (see S. Maruo, J. Microelectromechanical Systems, 7, pp. 411-415 (1998), and B. H. Cumpston et al., Nature, 398, pp. 51-54 (1999)).
The present invention is directed to a new method of manufacturing microscale devices that overcomes problems associated with traditional assembly, lithographic, and other methods. The present method permits the integration of several different microscale components, which can be manufactured from different materials of construction, into a single microscale device, without the need to assemble individual microscale components to form the device.
The present invention relates to methods of manufacturing microscale devices, to the microscale devices made by the method, and to methods of detecting a chemical or physical change, or a chemical or biological agent, using the microscale devices. More particularly, the present invention relates to a method of manufacturing microscale devices that is fundamentally different from prior manufacturing methods, solves problems and disadvantages associated with prior manufacturing methods, and retains advantages associated with prior manufacturing methods. In particular, the present method retains an advantage of a lithographic process (which avoids assembly) and retains an advantage of an assembly process (which permits integration of device components made from different materials of construction). The present manufacturing method also provides the ability to expand the functionality of microscale devices, and thereby expand the scope of microscale devices, both in types of devices and practical applications, beyond present-day limits.
Accordingly, one aspect of the present invention is to provide a method of manufacturing microscale components of a microscale device, i.e., a method of manufacturing individual microscale device components on or within a substrate to provide the completed microscale device. The microscale component can be a structural component of the device (i.e., a wall or channel of the device), or the microscale component can be a functional component of the device (i.e., a valve, a pump, an optoelectronic component, or a sensor, for example). A structural component is nonresponsive to physical and chemical changes, and to chemical and biological agents. A functional component can be responsive either to a biological agent (i.e., is bioresponsive) or to a physical or chemical change or a nonbiological chemical agent (i.e., is physio/-chemoresponsive).
Another aspect of the present invention is to provide a method of manufacturing a microscale device utilizing a substrate having one or more microscale channels, the properties of laminar fluid flow in a microscale channel, and polymerization of a polymerizable mixture at a preselected location within a channel. The substrate can have preformed channels, for example, channels prepared by lithographic techniques. Alternatively, the present method can be used to form the microscale channels in the substrate. In either embodiment, the present method is repeated as necessary to fabricate individual microscale components in the channels, from the same or different materials of construction, until manufacture of the microscale device is complete.
Yet another aspect of the present invention is to provide a method of manufacturing a microscale device wherein no manipulative assembly steps are required to form the microscale device from microscale components.
Still another aspect of the present invention is to provide a method of manufacturing a microscale device having a plurality of functional microscale components, wherein individual components can be manufactured from different materials of construction. Accordingly, microscale devices manufactured by the present method can be specifically designed for any of a variety of specific end use applications. The present method, therefore, greatly expands the number of practical applications for microscale devices.
Another aspect of the present invention is to provide a method of manufacturing microscale devices wherein development and manufacturing times are short, and the resulting devices are cost effective.
It also is an aspect of the present invention to provide microscale devices that perform as sensors, actuators, or detectors, and that provide a fast and accurate response to a preselected stimulus of interest, such as a chemical or biological compound, or a physical or chemical change, like a temperature or pH change. This aspect of the invention is achieved by manufacturing a microscale component having the appropriate functionality to respond to the stimulus of interest.
Another aspect of the present invention is to provide a microscale device capable of converting a microscale physical or chemical change, or a microscale amount of a chemical or biological agent, directly to a macroscale detectable response without the need for an external power source or other external means of converting a microscale event to a macroscale response. The microscale devices, therefore, are useful as portable detectors and sensors for physical or chemical changes, or for chemical and biological agents, for example, to detect or monitor environmental and food contaminants, changes in a chemical process, or disease treatment regimens.
Another aspect of the present invention is to solve a longstanding problem of bridging the gap between microscale and macroscale environments.
These and other aspects and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments taken in conjunction with the figures.